E M Barrett

Estimating the incidence of rheumatoid arthritis: Trying to hit a moving target

OBJECTIVE To examine the effect of delay between symptom onset and notification to an arthritis register and the effect of application of the American College of Rheumatology (ACR; formerly, the American Rheumatism Association) 1987 criteria in a cumulative manner on estimates of the incidence of rheumatoid arthritis (RA). METHODS General practitioners and/or hospital consultants in the Norwich Health Authority, Norfolk, UK, notified the Norfolk Arthritis Register (NOAR) of all patients who had onset of inflammatory polyarthritis (swelling of > or =2 joints) during 1990. The patients were assessed within 2 weeks of notification and annually thereafter. The ACR 1987 criteria for RA were applied at each assessment. Age- and sex-specific incidence rates were calculated. RESULTS If up to 12 months elapsed from symptom onset to notification to NOAR and the ACR criteria were applied at the baseline assessment, RA incidence estimates, age-adjusted to the population of England and Wales, were 30.8/100,000 for women and 12.7/100,000 for men. If up to 5 years elapsed from symptom onset to notification, these estimates rose by 45% for women and 36% for men. If up to 5 years elapsed between symptom onset and notification and the criteria were applied cumulatively, the estimates rose by 75% and 93% for women and men, respectively, compared with the 1-year data, reaching 54.0/100,000 for women and 24.5 per 100,000 for men. CONCLUSION Accurate estimation of the incidence of RA requires long-term followup of patients who present with undifferentiated inflammatory polyarthritis. The highest age-adjusted estimates from this study are probably the best that are available.

A simple algorithm to predict the development of radiological erosions in patients with early rheumatoid arthritis : prospective cohort study

Abstract Objective: To produce a practical algorithm to predict which patients with early rheumatoid arthritis will develop radiological erosions. Design: Primary care based prospective cohort study. Setting: All general practices in the Norwich Health Authority, Norfolk Subjects: 175 patients notified to the Norfolk Arthritis Register were visited by a metrologist soon after they had presented to their general practitioners with inflammatory polyarthritis, and again after a further 12 months. All the patients satisfied the American Rheumatism Associations 1987 criteria for rheumatoid arthritis and were seen by a metrologist within six months of the onset of symptoms. The study population was randomly split into a prediction sample (n = 105) for generating the algorithm and a validation sample (n = 70) for testing it. Main outcome measures: Predictor variables measured at baseline included rheumatoid factor status, swelling of specific joint areas, duration of morning stiffness, nodules, disability score, age, sex, and disease duration when the patient first presented. The outcome variable was the presence of radiological erosions in the hands or feet, or both, after 12 months. Results: A simple algorithm based on a combination of three variables—a positive rheumatoid factor test, swelling of at least two large joints, and a disease duration of more than three months—was best able to predict erosions. When the accuracy of this algorithm was tested with the validation sample, the erosion status of 79% of patients was predicted correctly. Conclusions: A simple algorithm based on three easily measured items of information can predict which patients are at high risk and which are at low risk of developing radiological erosions.

Benchmarking: the five year outcome of rheumatoid arthritis assessed using a pain score, the Health Assessment Questionnaire, and the Short Form-36 (SF-36) in a community and a clinic based sample

BACKGROUND Treatment, and therefore outcome, of rheumatoid arthritis (RA) will improve in the next few years. However, improvement in outcome can only be judged against the probability of certain outcomes with current conventional treatment. AIM To document the five year outcome of RA in the late 1990s. SETTING Norfolk Arthritis Register (NOAR). DESIGN Longitudinal observational cohort study. METHODS 318 patients with recent onset inflammatory polyarthritis recruited by NOAR in 1990–91 completed five years of follow up. Four groups were assessed: the whole cohort, all those referred to hospital, those who satisfied criteria for RA at baseline, and those referred to hospital who satisfied criteria for RA at baseline. Outcome was assessed with a visual analogue scale for pain, the Health Assessment Questionnaire (HAQ), and the Short Form-36 (SF-36). RESULTS Of the RA hospital attenders, 50% had a visual analogue scale pain score of 5 cm or less and an HAQ score of 1.125 or less. SF-36 scores were reduced in all domains. Results are presented as cumulative percentages. CONCLUSIONS These results can be used for comparison and to set targets for improvement.

Associations between demographic and disease-related variables and disability over the first five years of inflammatory polyarthritis: A longitudinal analysis using generalized estimating equations

OBJECTIVES To investigate whether the relationship between demographic and disease-related variables and disability is constant during the first five years of inflammatory polyarthritis (IP) and to identify the contribution from involvement of specific joint areas to overall disability. METHODS 684 patients referred to the Norfolk Arthritis Register were followed for five years using the Health Assessment Questionnaire (HAQ). The relationship between disability and demographic and clinical variables was analyzed using a multi-level modelling approach. RESULTS Female gender, older age at symptom onset (> or = 64 years), joint involvement at six specific sites, joint tenderness and the number of deformed joints were all independently associated with disability (HAQ > or = 1.00). Similar results were obtained using a more stringent cut-off (HAQ > or = 1.50) or when analysis was restricted to the 325 patients who satisfied the 1987 ARA list criteria for rheumatoid arthritis. CONCLUSION Disability, as measured by the HAQ, was associated with a large number of independent factors over the first five years of disease.

Occurrence of rheumatoid arthritis is not increased in the first degree relatives of a population based inception cohort of inflammatory polyarthritis.

OBJECTIVE: To determine the risk of rheumatoid arthritis (RA) in first degree relatives of a true population based sample of probands with inflammatory polyarthritis. METHODS: In a case-control study, a two stage screening procedure was used to ascertain the prevalence of RA in 518 first degree relatives of 207 Norfolk Arthritis Register cases registered in 1990 and 414 first degree relatives of 180 local controls. An initial joint symptom and medical history questionnaire was followed by a physical examination, and serological and radiological evaluation of those with symptoms. RESULTS: The prevalence of RA in the first degree relatives of all the Norfolk Arthritis Register cases was 7.7/1000, compared with 4.8/1000 in the first degree relatives of the controls, with a risk ratio of 1.6 (95% confidence interval 0.3 to 8.7). This very modest increase was also seen when the analysis was restricted to the first degree relatives of Norfolk Arthritis Register cases who satisfied the American Rheumatism Association criteria for RA: prevalence rate 7.2/1000. CONCLUSION: There was no evidence of an important increased familial risk of RA in this community based sample. These data are compatible with others from immunogenetic studies showing only weak HLA associations with community ascertained RA.

Low frequency of recent parvovirus infection in a population-based cohort of patients with early inflammatory polyarthritis

OBJECTIVE To determine the contribution of human parvovirus B19 infection in explaining the incidence of early inflammatory polyarthritis (IP) in a population. SETTING The Norfolk Arthritis Register (NOAR) is a community-based programme aiming to ascertain all new cases of IP arising in a population that lead to attendance at primary care. SUBJECTS 147 newly ascertained subjects with IP with a disease duration of less than 16 weeks. METHODS Full clinical appraisal of all subjects who were followed up for three years. B19 IgM assayed with a third generation antibody capture enzyme immunoassay. RESULTS Only four (2.7%) patients had evidence of recent B19 infection, only one of whom did not satisfy criteria for rheumatoid arthritis (RA). CONCLUSION B19 infection does not explain more than a small proportion of either RA or undifferentiated IP cases occurring in the population.

The existence of geographical clusters of cases of inflammatory polyarthritis in a primary care based register

OBJECTIVES To determine whether there is any evidence that there are spatial clusters of rheumatoid arthritis in particular, and inflammatory arthritis in general. METHODS Setting was a population based incidence register of inflammatory arthritis: the Norfolk Arthritis Register (NOAR). All cases identified between 1990–1995 were mapped to place of residence. Statistical evidence of clustering was determined by calculating Poisson probabilities in putative areas. RESULTS Three clusters were identified including one small area (population 85) where five unrelated cases developed during this time period. There was no obvious greater disease homogeneity within clusters and no common environmental factors were identified. CONCLUSION Rare clusters of inflammatory polyarthritis do occur. Their significance and cause remain to be elucidated.

The end of innocence

Elizabeth Barrett reflects on how she supported a communitys right to involvement